You can find a list of code terms in the BlockLauncher-App: settings-->Troubleshooting-->dump ModPE Script functions
You can find most of the code terms here (with explanations): https://github.com/Connor4898/ModPE-Docs/wiki
About adding textures: https://github.com/zhuowei/MCPELauncher/wiki/Including-textures-in-ModPE-scripts
Personally, I would recommend http://imnofox.com/zxc/
If you're on a PC, it has a really nice layout.